As sensors (rate gyroscopes) for detecting angular velocities, a vibratory gyroscope, a gas rate gyroscope, and the like are well-known. Moreover, for example, as described in Japanese Laid-Open Patent Publication No. 2000-66722 (hereinafter, referred to as patent document 1), there is a known technology in which a movable body is provided therein with a high-sensitivity gyroscope sensor having a relatively narrow detectable angular velocity range and a low-sensitivity gyroscope sensor having a relatively wide detectable angular velocity range, so as to allow selective switching between the low-sensitivity gyroscope sensor and the high-sensitivity gyroscope sensor according to the magnitude of the angular velocity generated in the movable body, whereby the angular velocity can be measured in a wide range.
Now, for example, a biped moving robot is provided therein with an angular velocity measuring device such as a rate gyroscope for its posture control. In this case, although a conventional biped moving robot has performed relatively slow movements such as walking or bowing, in recent years there has been a demand for a rapid movement of the robot such as running or kicking a ball. To make the biped moving robot perform this kind of movements, there is a need to control the posture of the biped moving robot to a desired position quickly and reliably. Therefore, the angular velocity measuring device to be mounted on the robot has been required to be rapid in response with a measurement to a change in angular velocity (to provide a measurement that rapidly changes in response to an abrupt change in angular velocity) and to provide stably high accuracy of a measurement for a steady angular velocity.
Various conventional rate gyroscopes, however, as angular velocity measuring devices have both advantages and disadvantages, and therefore have not been able to fully satisfy the above requirements. Describing this point, a general vibratory gyroscope includes a hard solid such as crystal, which is advantageous to electrical conversion, in a deformable body, namely, a portion deformed by an angular velocity applied to the sensor. Therefore, the vibratory gyroscope is rapid in response to the angular velocity. The vibratory gyroscope, however, is affected by a factor that changes the shape of the deformable body even if it is a disturbance independent of the angular velocity such as a temperature change, if it occurs, and thus it appears as drift in an output of the vibratory gyroscope. On the other hand, a gas rate sensor detects a deflection of a gas stream relative to a pair of heat wires, which are located downstream in a passage, as an angular velocity by generating the gas stream in the passage and using it as a deformable body. Therefore, in the gas rate sensor, changes in the shape of the passage caused by, for example, a thermal expansion or the like will not affect the detection of the angular velocity, unless there is any deflection in the gas stream. The gas stream of the gas rate sensor, however, is inferior in followability to a solid as a deformable body, and therefore it is not adequate to detecting a high-frequency angular velocity.
It is also conceivable to use detected outputs of two sensors different in characteristics, with selective switching between the detected outputs by using the technological concept as described in the patent document 1. If so, however, angular velocity measurements are apt to be discontinuous at the time of switching between the detected outputs of the sensors. In addition, switching between the detected outputs lags behind an abrupt change in angular velocity, and therefore it is hard to secure response with measurements to the angular velocity. Thereby, it is hard to appropriately control quick movements of the biped moving robot even if these measurements are used for the posture control of the biped moving robot.
As angular velocity sensors, which are good in response and generate a stable detected output for a steady angular velocity, there have already known a ring laser gyroscope, a fiber optical gyroscope, and the like. All of them, however, have been expensive in comparison with the vibratory gyroscope and the gas rate gyroscope.
In view of the background set forth in the above, the present invention has been provided. Therefore, it is an object of the present invention to provide an angular velocity measuring device, having high response and stability in angular velocity measurements, at a low price. It is another object of the present invention to provide a leg-moving robot capable of controlling the posture appropriately.